Hydrogels as next-generation anti-corrosive coatings: design, mechanisms, and prospects

Abstract

Metal corrosion poses a persistent global challenge across industries, driving the search for advanced protective systems that surpass the limitations of conventional protective coatings. Hydrogels, owing to their unique characteristics, have emerged as promising coating materials for addressing the bottlenecks of conventional anti-corrosive coatings. Although hydrogel-based coatings have demonstrated certain corrosion-resistant properties, many critical challenges, such as inadequate mechanical strength, poor long-term stability under harsh conditions, and limited durability during service, remain unsolved. To develop more effective hydrogel-based anti-corrosion systems, it is essential to systematically investigate hydrogel synthesis strategies, application methods on metallic substrates, and the dynamic response mechanism of hydrogel coatings to external stimuli. Accordingly, the first section of this review details the preparation processes of hydrogels and proposes potential improvements based on a critical analysis of their advantages and technical limitations. The second section dissects the dual protective mechanisms of hydrogel coatings as (1) resilient physical barriers that impede corrosive species and (2) active protection systems that enable controlled release of corrosion inhibitors and intrinsic self-healing via dynamic bonds. We systematically present the application advances, categorizing hydrogel usage as direct coatings, composite fillers, and inhibitor reservoirs. Special emphasis is placed on material compatibility, inhibitor release kinetics, and strategies for optimizing self-healing performance. This review concludes by outlining future research directions, emphasizing the need for robust interfacial adhesion, multi-functional design, and stimulus-responsive systems to bridge the gap between laboratory innovation and practical, industrial applications.